The following patent document 1 discloses a tire vulcanizing apparatus comprising a side mold segment, a tread mold segment, and a heater part. The side mold segment has a side-shaping-face for shaping the outer surface of the tire sidewall portions. The tread mold segment is for shaping the outer surface of the tire tread portion. The heater part is for heating the side mold segment and the tread mold segment to vulcanize the raw tire. The vulcanization apparatus is provided in the side mold segment with a void space extending along the side-shaping-face. Such void space can reduce the heat transfer from the heater part to the sidewall portion. Thereby, the tread portion having a larger thickness and the sidewall portion having a smaller thickness can be vulcanized evenly.
However, even in such tire vulcanizing apparatus, if the vulcanizing time is long, the temperature of the void space becomes increased near to the vulcanization temperature, and the heat transfer to the sidewall portion can not be reduced. As a result, there is a possibility that the sidewall portion is over-vulcanized. Therefore, in the tires manufactured by the use of such tire vulcanizing apparatus, there is a problem with the durability and rolling resistance.
Patent document 1: Patent Application Publication No. 2013-237199